This project involves the determination of the 3-dimensional crystal structure of two insecticidal toxins produced by the soil bacterium Bacillus thuringiensis, CytA and CryIIA. These toxins are of import to agriculture as natural insecticidal agents. Since the putative mode of action of these toxins is the formation of cation-selective channels in the planar lipid-bilayers of insect gut epithelial cells leading to colloid osmotic lysis, their structures should shed light on the mechanism of pore formation. The Computer Graphics Laboratory resource has been used for the purpose of visually solving heavy atom Patterson maps leading to initial protein maps. In addition CGL has been used for characterization of map quality, chain tracing, and sequence assignment in electron density maps leading to starting structures subjected to crystallographic refinement.